A study of the modulation capabilities of the Cs‐Ba tacitron with different grid designs was made. Results showed the ignition grid potential to be independent of grid design at a modulation frequency, fg, of 1 kHz. At fg=22 kHz, discharge ignition with a 26% transparent grid was harder to achieve than at fg=1 kHz. The grid design greatly affects not only the extinguishing potential, but also the forward voltage drop. Increasing the grid transparency and/or aperture size makes it harder to extinguish the discharge (increases ‖ Vg− ‖), but lowers the forward voltage drop across the tacitron. Increasing fgalso increases ‖ Vg− ‖, but lowers the forward voltage drop across the tacitron. Increasing fgalso increases ‖ Vg− ‖ and lowers the range of Cs pressure for stable current modulation. For a TOPAZ‐II type space nuclear reactor power system (SNPS), the lowest electrical power consumption by Cs‐Ba tacitrons inverters, employing 34% transparent, 0.5 mm diameter holed grid and operating at IC=10 A or 20 A and fg=1 kHz, is ∼6.5% of the total system output power. This electrical power consumption includes that of the grid power supply and the power loss in the tacitron during discharge. © 1995American Institute of Physics